Changiz Ghobadi

Islamic Azad University, Teheran, Tehrān, Iran

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Publications (87)56.92 Total impact

  • Maryam Majidzadeh · Changiz Ghobadi · Javad Nourinia
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    ABSTRACT: This paper proposes a novel reconfigurable frequency selective surface (FSS) structure for ultra-wide band (UWB) and multi-band applications. The proposed structure is a simple single layer FSS printed on 10 mm × 10 mm × 1.6 mm FR4 substrate. This structure embraces a simple square loop on the front side of the substrate whereas; another one along with two vertical arms is incorporated on the backside. Innovatively, a wise combination of diodes is embedded on the substrate's backside which are handled through a DC feed line circuit. By an effective diodes switching, three operating modes are attained. In the context of UWB filtering, the proposed FSS contributes in remarkable rejection of UWB frequencies through the “ON” state of all diodes. However, assigning a specific set of diodes in “ON” state provokes multi-band operating mode in which WiMAX, WLAN, and Ku bands are rejected. Moreover, setting all the diodes at “OFF” state extends the rejection capabilities by dismissing an additional frequency range. Furthermore, a remarkable notice relates to higher attenuation in shielding effectiveness (SE) acquired for rejection bands. Extensive numerical and experimental studies are devised to found a suitable comparison platform. The close agreements between the obtained results are acknowledging the suitable performance of the proposed FSS.
    No preview · Article · Nov 2015 · AEU - International Journal of Electronics and Communications
  • Changiz Ghobadi · Maryam Majidzadeh
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    ABSTRACT: A novel dual band notched antenna is presented in this paper. First, an Ultra Wide Band (UWB) antenna structure with a rhombic radiating patch and a simple ground plane is proposed. Then, aiming at the filtering of interfering frequency bands from UWB frequency range, two pairs of joint slots are embedded in the antenna body. By the inclusion of these slots, surface current distribution is disturbed at the vicinity of the slots and as a result, 5.15-5.825GHz Wireless Local Area Network (WLAN) band and 8.025-8.4GHz International Telecommunication Union (ITU) band are rejected. In the next step, with the aim of comparing the presented antenna with the previously designed structures regarding different features such as size, bandwidth, gain variations and number of the filtered frequency bands simultaneously, an efficient framework is established. The proposed method is based on Analytical Hierarchy Process (AHP) that is one of the Multi Attribute Decision Making (MADM) techniques. The design process, simulation and measured results, and the AHP based method will be discussed in detail.
    No preview · Article · Oct 2015 · Journal of Intelligent and Fuzzy Systems
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    ABSTRACT: In this paper, we introduce a compact microstrip band-stop filter (BSF) at X-band communication and this shall be used in local oscillator chain for X-band transceiver due to its simple structure, compact size, and excellent performance. Presented microstrip filter consists of a transmission line with a square ring stub and four arrow-shaped strips protruded inside the ring, and a ground plane. Operation frequencies of the filter can be easily controlled by changing four protruded arrow-shaped strips in the square-ring stub. The proposed band-stop filter has wide bandwidth from 8 to 12 GHz for X-band communication that can be used in radar applications. Experimental results show good agreement between simulation results and measurements that excellent stop-band performance could be obtained through the proposed band-stop filter. The proposed microstrip filter is fabricated on a Rogers RT/Duroid 5880 substrate with a relative dielectric constant of 2.2 and has a very small size of 10×15 mm2.
    No preview · Article · Apr 2015 · Applied Computational Electromagnetics Society Journal
  • Davod Ahmadian · Changiz Ghobadi · Javad Nourinia
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    ABSTRACT: A new tunable plasmonic biosensor is proposed by embedding liquid crystals in the slit region of a corrugated plasmonic nanoslit array. The absorption spectrum of the structure and, thus, the sensing wavelength can be controlled by applying voltage to the electrode parts of the device. The interaction between the waveguide mode inside the slit and the surface plasmon polaritons on the corrugation surface can be modified using the electrooptical effect of the liquid crystals. Our numerical simulations with the finite-difference time-domain (FDTD) method reveal a large tuning of the absorption spectrum up to 100 nm. In addition to the tunability feature, the structure has a high sensitivity of 570 nm/RIU. The sensing performance of the device is evaluated by performing homogeneous biochemical sensing simulations. The special feature of the proposed structure gives it an opportunity to be used as an efficient element in integrated photonics circuits for miniaturization and tuning purposes.
    No preview · Article · Apr 2015 · IEEE Photonics Journal
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    ABSTRACT: A new approach for designing a single-feed circular microstrip antenna with dual-band/multi-band circularly polarized (CP) radiation are demonstrated and studied experimentally. It is presented that by embedding pairs of asymmetrical ring-shaped arc slots to the boundary of both circular patch and the ground plane the impedance bandwidth of the antenna increases. This can be achieved by making use of both mutual coupling between the resonances of the ring-shaped arc slots and the fundamental resonances of the circular antenna. Also, by extending the ring-shaped arc slots out with narrow slots, the circular microstrip patch antenna can perform dual-band/multi-band CP radiation. Further details of the proposed CP microstrip antenna designs are described, and typical experimental results are presented and discussed.
    No preview · Article · Jan 2015 · International Journal of Microwave and Wireless Technologies
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    ABSTRACT: A novel compact antenna with Circular Polarization (CP) characteristics is presented. The antenna structure includes an asymmetrical rectangular radiating patch from which a semi-circle shaped slot is cut. A 50 Ω Co- Planar Waveguide (CPW) feed line with two rectangular slots feeds the antenna. Two inverted L-shaped strips and also two spiral shaped slots are embedded on opposite corners of the ground plane to further enhance the antenna bandwidth and also generate the circular polarization property. The antenna is printed on a compact size FR4 substrate with the total dimensions of 20×20×1.6 mm3. The proposed antenna operates over the frequency range of 3-14.5 GHz for VSWR<2 and exhibits CP in 5.35-7.65 GHz (35%).
    No preview · Article · Jan 2015 · Applied Computational Electromagnetics Society Journal
  • K. Athari · C. Ghobadi · M.A. Layegh · J. Nourinia
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    ABSTRACT: A novel coplanar waveguide (CPW)-fed monopole as a radiating element of an antenna is proposed for chip size realization. The antenna has been designed on the basis of the elliptical geometry. The proposed CPW slot antenna is compact with the size of 26×36×1.6 mm3 which is printed on a cheap substrate of FR-4 and also is smaller than the previously proposed antennas. The parameters of this antenna were optimized through numerical simulations in Ansoft HFSS, after which the antenna was fabricated and characterized. The measurement results show that the proposed antenna has a -10 dB return loss bandwidth of 5.12 to 5.91 GHz, which covers the entire required band for Worldwide Interoperability for Microwave Access (WiMAX) and Wireless Local Area Network (WLAN) 802.11a standard.
    No preview · Article · Dec 2014
  • Farzad Alizadeh · Changiz Ghobadi · Javad Nourinia · Rasoul Zayer
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    ABSTRACT: This letter presents a broadband, high efficiency patch antenna that utilizes a novel complementary split ring resonators(CSRRs) embedded on the ground plane. The demonstrated approach results in a significant improvement in impedance bandwidth, efficiency, compactness and directivity in comparison to a conventional microstrip antenna. A coaxial-fed microstrip antenna(MA) is integrated with a simple CSRRs structure that is cut from the ground plane. Then, two crossovers are introduced to the conventional CSRRs structure in order to both compactness of the structure and reverse the current flow along the strips. Inserting crossovers with via bridges to the CSRRs structure facilitates a nearly complete impedance match to the source over a wider bandwidth and also maintain a high, 89%, radiation efficiency. The designs and their performance characteristics were simulated with the High Frequency Structure Simulator (HFSS) and verified using the time domain CST Microwave studio simulator and Sonnet EM software. Test results of the fabricated designs show a good correlation with simulated outcomes, validating the design principles.
    No preview · Conference Paper · Sep 2014
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    ABSTRACT: Breast cancer is one of the most prevalent non-skin-related malignancies among women in the world. Thus, many countries have commenced screening test in early stages in order to diagnose breast cancer. Buried object detection is performed in the present work to detect 3-D breast cancer applying SVM classifier. Some transmitters and receivers are located above the breast. Each transmitter radiates monochromatic electromagnetic wave.
    No preview · Article · Sep 2014 · Journal of the Liaquat University of Medical and Health Sciences
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    ABSTRACT: A compact reconfigurable microstrip slot antenna with switchable single and dual band notch functions for ultrawideband (UWB) applications is presented in this study. In the proposed structure, an additional resonance is excited by etching two symmetrical notches on the feed-line and thereby a UWB characteristic is obtained. Then, by cutting two slots on the radiating patch and embedding two positive-intrinsic-negative (PIN) diodes along these slots, switchable single and dual band notch performances are added to the antenna performance. By changing the bias states of the PIN diodes, the antenna is capable of exhibiting four different performances of UWB spectrum coverage, UWB coverage with single rejection of the wireless local area network (WLAN) band, UWB coverage with single rejection of the WiMAX and C-band spectrum, and UWB coverage with dual band notch function at the WLAN, the WiMAX and the C-band frequencies. Good agreement between the simulated and the measured results is achieved at different performances of the antenna. The designed antenna has a small size of 20 ?? 20 mm2 and the measured results reveal that the fabricated antenna has good radiation behaviour in the UWB frequency spectrum with switchable band notch functions at 3.15-3.85 and 5.43-6.1 GHz which can eliminate the UWB frequency band interference with the WiMAX, the C-band and the WLAN systems.
    No preview · Article · Jun 2014 · IET Microwaves Antennas & Propagation
  • Mahmood Abbasi Layegh · Changiz Ghobadi · Javad Nouri Nia

    No preview · Conference Paper · May 2014
  • Source
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    ABSTRACT: A novel printed planar monopole antenna for LTE multi-input and multi-output (MIMO) application is proposed. By adding six ellipticals on top of the antenna, we enhance the lower frequency bandwidth. The idea for this is gotten from [1, 2]. These papers designed by using log periodic technique with the number of rectangle and flare elements . Also, by cutting E-shaped slots in the ground plane, additional resonance is excited, and hence much wider impedance bandwidth can be produced. The proposed antenna provides all of the LTE bands between 0.65 GHz to 4 GHz. In order to provide low mutual coupling and envelope correlation, two of the antennas are combined with orthogonal polarizations. The mutual coupling and envelope correlation coefficient (ECC) of the antenna are lower than -21 dB and 0.002 across the operation bands, and total active reflection coefficient (TARC) is less than 0.35. The designed antenna has small size area of 55 × 94 mm 2 , which has a small size with respect to recently reported antennas. Index Terms -Long term evolution (LTE), multi-input and multi-output (MIMO), monopole antenna, and mutual coupling.
    Full-text · Article · Jan 2014 · Applied Computational Electromagnetics Society Journal
  • Maryam Majidzadeh · Javad Nourinia · Changiz Ghobadi
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    ABSTRACT: A novel co-planar waveguide (CPW)-fed antenna with circular polarization (CP) characteristics in the 5.1 GHz - 5.8GHz is presented. By adding a vertical stub and a rotated L shaped stub to the antenna structure, a bandwidth of 5 GHz - 8GHz (46%) for S11 < -10 dB is achieved and also circular polarization characteristics is generated in the 5.1 GHz - 5.8 GHz, which completely covers the wireless local area network (WLAN) frequency band. The antenna has a very simple structure and occupies a compact area of 25 × 25 × 1 mm3. The very simple structure and small size are of the marvelous merits of the proposed antenna. The antenna design process, impedance bandwidth and axial ratio (AR) bandwidth enhancement process are discussed in detail.
    No preview · Article · Oct 2013 · Applied Computational Electromagnetics Society Journal
  • S. Bashiri · Ch Ghobadi · J. Nourinia · M. Ojaroudi
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    ABSTRACT: This paper proposes a novel slot-like sleeve-monopole antenna for ultra wideband applications with multi-resonances performance. The antenna consists of a CPW-fed sleeve monopole antenna with a coupled inverted U-shaped strip, surrounded by a pair of folded strips, which provides a wide usable fractional bandwidth of more than 120% (3.09 GHz - 12.86 GHz). By adding a coupled inverted U-shaped strip with variable dimensions on the radiating patch and also by inserting two folded strips, additional resonances are excited and hence much wider impedance bandwidth can be produced, especially at the higher band. The designed antenna has a small size of 30 × 30 mm2. Simulated and experimental results obtained for this antenna show that it exhibits good radiation behavior within the UWB frequency range.
    No preview · Article · Sep 2013 · Applied Computational Electromagnetics Society Journal
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    ABSTRACT: In this paper, a compact ultra-wideband (UWB) band-pass filter with sharp roll-off and improved out-of –band performance is designed and manufactured. In the proposed structure, modified one quarter-wavelength cross-shaped coupled lines (CCLs), and also radial stub loaded resonator (RSLR), are implemented in order to reduce the total size of the UWB BPF. The RSLR is able to control two tuneable transmission zeros (TZs) separately and the CCLs can be properly designed so that the unwanted pass band is rejected. A prototype of the proposed UWB BPF is fabricated and tested. The measured results are in good agreement with the simulated data and the proposed structure shows a sharp selectivity and good filtering performance in the frequency band of interest. Keywords: Band-pass filter (BPF), Cross-Shaped Coupled Lines (CCLs), multiple-mode resonator (MMR), radial stub loaded resonator (RSLR), stub-loaded resonator (SLR), ultra-wideband (UWB).
    Full-text · Conference Paper · May 2013
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    ABSTRACT: This letter presents the investigation results on a novel circularly polarized square-slot antenna (CPSSA) array designed to operate at a frequency of 5.5 GHz. In order to realize the proposed antenna array, four miniature circular polarized square-slot antennas are used with L-shape grounded strips located at the slots' opposite corners to reduce cross polarization. The antenna is fed by symmetric coplanar waveguide. The CPSSA element achieves a bandwidth of 16.6% for an axial ratio ≤ 3 dB. The CPSSA's performance is further enhanced with the construction of a novel 2 × 2 antenna array that is designed using sequentially rotated feed technique. The 3-dB axial ratio of the array extends to approximately 2 GHz with an impedance bandwidth of 31%. The CPSSA array was designed to operate over the frequency range between 4 and 6.825 GHz corresponding to an impedance bandwidth of 52% for VSWR
    No preview · Article · Jan 2013 · IEEE Antennas and Wireless Propagation Letters
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    ABSTRACT: A compact broadband circularly polarized elliptical slot antenna (CPESA) composed of two linked elliptical slots is presented. In order to realize the proposed CP antenna, two rectangular stubs are embedded in the feedline structure to excite two orthogonal E vectors. By embedding two rectangular stubs in the feedline structure and removing of four rectangular slits from the ground plane, the return loss and the axial-ratio (AR) bandwidths are noticeably increased. The designed CPESA with the compact size of 20 × 20 × 1 mm3 operates over the frequency band between 4.3-8 GHz (60%) for and exhibits a 40% (4.3-6.5 GHz) CP bandwidth. Throughout this letter, the design process of the proposed antenna is presented and discussed in detail .
    No preview · Article · Jan 2013 · IEEE Antennas and Wireless Propagation Letters
  • Maryam Majidzadeh · Changiz Ghobadi · Javad Nourinia

    No preview · Article · Jan 2013
  • Maryam Majidzadeh · Javad Nourinia · Changiz Ghobadi

    No preview · Conference Paper · Jan 2013

  • No preview · Article · Jan 2013 · Wireless Engineering and Technology

Publication Stats

1k Citations
56.92 Total Impact Points

Institutions

  • 2010-2015
    • Islamic Azad University
      • Department of Electrical Engineering
      Teheran, Tehrān, Iran
  • 2004-2015
    • Urmia University
      • • Group of Electronic Egineering
      • • Department of Electrical Engineering
      Rezâiyye, Āz̄ārbāyjān-e Gharbī, Iran
  • 2012
    • Islamic Azad University of Urmia
      • Department of Electrical Engineering
      Rezâiyye, Āz̄ārbāyjān-e Gharbī, Iran